The invention relates to a device for treating a gas laden with pollutants, comprising at least one adsorption module for adsorbing the pollutants, which is utilized in an adsorption apparatus and contains at least one electrically conductive layer of an activated carbon fiber mat, comprising an electric current circuit for heating the activated carbon fiber mat for the desorption of the adsorbed pollutants, and comprising a distributing pipe, which is routed into the center of the adsorption module and has outlet openings, for a flush gas for inertizing and rinsing the activated carbon fiber mat.
The invention also relates to a method for treating a gas laden with pollutants, wherein the gas is applied to at least one adsorption module, which comprises an activated carbon fiber mat or an activated carbon fiber wrap-around, within an adsorption apparatus, the gas is uniformly distributed along the axial length of the module, whereby the pollutants are adsorbed on the activated carbon fibers and, after having been charged with pollutants, the activated carbon fibers are regenerated by heating the activated carbon fibers by conducting an electric current therethrough, and the pollutants are subsequently flushed out of the activated carbon fibers using an inert flush gas.
The prior art has long included adsorbing pollutants in gases on activated carbon and regenerating this activated carbon for a new adsorption process. The activated carbons utilized for this purpose are primarily in the form of fillings made of granulates in fixed beds, or activated carbon fibers in the form of nonwoven fabrics, woven fabrics, or knitted fabrics.
DE 100 32 385 A1 describes a method for regenerating electrically conductive adsorbents laden with organic substances, which are heated by conducting electric current therethrough. The adsorbent is heated, alternately and in temporal succession, by conducting electric current therethrough, with no flush gas conducted through the adsorbent and, subsequently, with the electric current switched off, a flush gas is conducted through the adsorbent, by way of which, the adsorbed organic substances are expelled and the adsorbent is simultaneously cooled.
The prior art also includes a method for adsorption and regeneration using an adsorption unit, which includes at least one activated carbon fiber element, wherein the activated carbon fiber element is heated by current flow (EP 1 284 805 B1). The activated carbon fiber element is designed in such a way that the activated carbon fiber element forms a sufficient electric resistance for heating. A gas flow is conducted into the heated activated carbon fiber element in order to selectively adsorb at least one component of the gas flow. An adsorbed component is desorbed in the presence of an inert gas flow by means of the control or regulation of the temperature of the activated carbon fiber element to a temperature for the desorption using an electric current flow. The adsorption system for the method comprises a hollow housing in which at least one elongate, annular activated carbon fiber element is disposed, which has a ratio of length to cross section that is sufficient for achieving an electric resistance for heating, and includes an electric connection to the activated carbon fiber element and gas connectors for the inflow and outflow of the gas, into and out of the hollow housing, wherein the gas connectors are disposed in such a way that the gas is directed into the hollow activated carbon fiber element, penetrates therein, and flows through the volume.
In addition, EP 0 532 814 B1 describes a device for treating a fluid having at least one constituent contained therein. This known device has a structure made of an adsorbent material to be traversed by a flow of the fluid so as to adsorb the adsorbable constituent by the adsorbent, wherein the structure is disposed in a treatment vessel. The device comprises means for periodically regenerating the adsorbent material by the Joule-Thomson effect, wherein means are used for cooperating with the structure during a desorption phase consisting of passing an electric current through at least one of the layers of the structure. The structure comprises layers, which are superimposed in a zigzag shape, of connected, electrically conductive activated carbon, which is obtained by weaving electrically conductive fibers. The layers are spaced apart from each other, so that turbulences are generated when the fluid to be treated flows therethrough. The electric current flows through the fibers in the fiber direction (longitudinally) by way of the potential difference being applied at the ends of the layers made of activated carbon or at the ends of each layer. The gas to be treated is fed through a perforated pipe and into the layer wound around the pipe.
In addition, DE 41 04 513 C2 describes an adsorber made of adsorbent material, which is electrically conductive and can be heated by means of electric current to a temperature at which the adsorbent material is cause to desorb. Pressed or fibrous activated carbon, which is present in the form of tubes, hollow fibers, or mats, through which the pollutant-laden fluid can flow, is used as the adsorbent, electrically conductive material. The tubes, hollow fibers or mats are clamped, at the end faces thereof, between two electrodes, and current flows through them in the longitudinal direction thereof.
U.S. Pat. No. 4,737,164 A describes a method for recovering volatile impurities from gases, wherein the gas flows through an activated carbon fiber fabric, which is rolled up and is heated by means of a DC current in order to increase the adsorption capacity thereof, and for desorption. The rolled-up activated carbon fiber fabric is connected, on the end face thereof, to an electrode, which is connected to the DC voltage source.
In addition, DE 698 27 676 T2 describes an electrically regenerable air filter medium, which contains:                (A) an electrically conductive filter medium comprising a carbon fiber composite molecular sieve for the adsorption of impurities from a non-acceptable, inflowing air flow, and permitting the outflow of an acceptable air flow, wherein the filter medium made of a carbon fiber composite molecular sieve is an activated carbon fiber composite material, which further contains multiple porous carbon fibers, which are bound, by means of a carbonizable organic binding agent, in an open, permeable structure, and wherein the composite material has a porosity, before activation, in the range of approximately 82-86% and a surface area of more than 1000 m2/g;        (B) a regenerating means comprising a generator for electric current, which causes electric current to flow through the filter medium in order to desorb the adsorbed impurities from the filter medium; and        (C) an encapsulation means for conducting the desorbed impurities away from the acceptable air.        
All these known solutions have the disadvantage that electric current is applied to the activated carbon fibers along the longitudinal extension thereof (fiber axes), by way of which a non-uniform heating of the activated carbon fibers is induced along the axial length thereof in the adsorber module, and therefore the desorption of the pollutants from the activated carbon fibers is adversely impacted and can even remain incomplete. Adsorber modules having mats, hollow fibers, or tubes of activated carbon fibers utilizing electric regeneration have therefore not proven to be successful so far.
In addition, these adsorber modules having hollow fibers, tubes or wrapped-around mats made of activated carbon fibers induce a different pressure distribution of the gas along the axial length thereof, which results in a non-uniform flow profile and a non-uniform charging, having areas of local saturation, thereby resulting in a poor ratio of adsorber surface available to be traversed by flow and the adsorber surface area actually traversed by flow.
In addition, electrostatic discharges occur while the pollutant-laden gas flows through the mats, hollow fibers, and tubes made of activated carbon fibers, which results in the danger that uncontrolled electric shocks and discharges can cause fires and endanger the safety of the adsorption system.
Moreover, the hollow fibers, tubes, and wrapped-around mats made of activated carbon fibers do not have sufficient mechanical stability and are not easy to handle for purposes of maintenance and replacement. The known adsorber modules therefore tend to be susceptible to interference, and have an unsatisfactory efficiency and, therefore, are ultimately non-cost-effective.